Robert Dicke

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Abstract

A narrowly focused interview on Dr. Dicke's perspective on the field of cosmology and astrophysics at that time in his career, mostly relating to gravitation and relativity.

Transcript:

Weart:

This is not a formal history interview. Nobody will use this; nobody will quote it or cite it without your permission and so forth. It’s really mainly just for my own reference purposes. I guess the period. I’d like to cover with you is sort of the period when you have been active, which I guess goes back to around 1946 or whatever.

Dicke:

Yes, well, I never have been a real cosmologist, as such. There’s not a great deal I can do to help you on that.

Weart:

No, but you’ve been — I’m interested in you because you did have sort of an outsider’s perspective of the field. You have a physicist’s perspective, rather than an astronomer’s. I’ve mostly been talking with astronomers. I’d be particularly interested in things like the growth of interest in relativity, things like that. So, I don’t know what the best way to start is. Maybe I could just as you what you think have been the main trends, that you’ve been aware of, that you’ve been interested in, in the general areas of cosmology, astrophysics and so on, since the war.

Dicke:

Yes, well, I can tell you how long I’ve been interested in the field, that might be —

Weart:

Yes, I’d be particularly interested.

Dicke:

I guess a good place to start on this is, the work that I did back in World War II, with the development of the microwave radiometer.

Weart:

At the Red lab.

Dicke:

The Red Lab, where we made measurements on water vapor absorption in the atmosphere, and in the analysis of that, you looked through the water, you looked through the atmosphere at various elevation angles.

Weart:

Right.

Dicke:

And it was possible, from analyzing the data, to determine — it should have been possible, if you’d had real good accuracy and absolute accuracy, to determine how much radiation was coming in from space. And all we could do without data was set up a limit of about 20 degrees of the temperature radiation coming in. Well, at the time — and this number was published in a paper on the atmosphere absorption — at the time this was done, I really wasn’t thinking about a fireball radiation. At the time, I was really thinking about possibility of radiation from the distant Galaxies.

Weart:

Integrated over the —

Dicke:

Integrated, over the past history of the universe, but in a sense, radiation coming from galaxies. My interest in cosmology actually developed as an outgrowth of my interest in gravitational problems.

Weart:

Maybe I should ask first, how did you come to get interested in gravitational problems? Because I think you were doing it at a time when very, few people showed much interest in those problems.

Dicke:

That’s right. I recall as a graduate student, asking one of my professors about relativity ant gravitation, and he gave me the distinct impression that this really wasn’t part of physics. Interesting physical effects were so weak, you couldn’t — it’s almost impossible to measure them.

Weart:

Was this some experimentalist?

Dicke:

Well, that’s the theorist, it was [???] Bascow. But at the time I was a graduate student, there had been this long period of development of relativity and Einstein’s attempt to make a unified field theory, and so on. And there had been no new observations for a long period of time. On the cosmology end, people were making cosmological, models, paper after paper on cosmological models, but with no particular bearing on the observations. Couple of radio astronomy, expansion of the universe. There hadn’t been any real [???] on getting at questions of space closure, and — Well, on the question of interest in gravitation, I got interested in this when I was on sabbatical leave at Harvard. And —

Weart:

— that would have been —?

Dicke:

That was about 1954, ‘55, something like that. I’d been doing precision measurements of microstructure, that type of thing, making attempts to measure the more important numbers of these micro techniques, and was interested in looking around a little bit at that time. So it occurred to me that there was one experiment that was very important to relativity theory that had not been carried out with modern techniques. That was the [???] experiment. [Frisch ?] and his colleagues had done a very good job. It was towards the end of the 19th century, early 20th, and there had not been any done since then.

Weart:

How did you happen to notice this? You must have had some interest. Was it just that you were looking through the various fundamental measurements?

Dicke:

No. I don‘t know how. Perhaps in connection with some of my reading. I think I got ahold of Whittaker’s book on theories of the ether, which was a rather interesting book, and started thinking about gravtationa1 problems, and realized the crucia1 role that this particular experiment plays in sorting theories out. So I decided modern techniques had to be brought to bear on that. I didn’t realize at the time how hard this was going to be. We’ve been at this for years. It’s been a very successful experiment.

Weart:

It’s not like you could immediately apply laser or microwave techniques or something to it?

Dicke:

No. I had to develop a new technique. And it just took time. But we were able to make a substantial improvement over the old experiments. It was a significant experiment in that sense. And this is a rather crucial experiment, because it comes into gravitational theory in a number of ways. More than just the question of bodies, whether bodies fall with the same acceleration, is involved here. The implications of this, in terms of the internal structure of an atom being independent of when you put it, ant the ratios of masses of elementary particles not varying with position — those are questions you can raise and answer at a certain level with this experiment. I got interested in the, rather early in the philosophical question of the role that Mach’s Principle plays in connection with relativity theory and gravitational theory.

Weart:

Were you interested in this already when you were a graduate student, or you became — was it in the fifties that you became interested?

Dicke:

No, I think that — when did I get interested in that? It was in the fifties. It was not — no, I don’t think I really thought about it till the middle fifties, about. I saw that one way of interpreting this: at least, seemed to require a scalar component in the gravitation, which led to the scalar-tensor theory — which was actually only a modification of the theory that [???] had constructed earlier.

Weart:

After you did the [???] experiment, then you began to become interested in these other possible approaches.

Dicke:

Yes.

Weart:

So it came in very much from the theoretical, philosophical side?

Dicke:

Yes, that’s — I think Mach’s Principle rather early was a kind of a strong motivation for work in the area, and led to both the — I can’t say that it had a direct experiment on doing the [???] experiment. That was a rather more direct experimental interest. But very definitely, in my work on the scalar -tensor theory, it was —

Weart:

This represented sort of a shift for you, from experimental to theory, didn’t it? You hadn’t done much theoretical work?

Dicke:

I’d actually written theoretical papers before that. There was the one, for example, on the role of coherences, super-radiance paper, which I wrote in —

Weart:

— oh, that’s right, with the sort of pre-laser —

Dicke:

Pre-laser stuff. That paper just seems to — keeps influencing the literature.

Weart:

There’s another reference to it?

Dicke:

There’s one I just received yesterday.

Weart:

Super-radiance. I see.

Dicke:

That’s an ancient paper, but it keeps having its usefulness, even now.

Weart:

Right, I see the reference —

Dicke:

Well, let’s see. That’s off the track. Now, let’s see, what was I going to say? After realizing that the, at least the way I was interpreting it, the scalar field played a rather crucial role, with Mach Principle, then I noticed the implication of the weakening gravitation, at — with time — with the changing structure of the universe, as the universe grew older, then the scalar field would increase to a far weaker gravitational constant. This carried — this, implication carried with it the whole — a whole host of cosmological implications, which I started, at that point, really started to get interested in both geophysics and astrophysics. Up to then, I hadn’t been.

Weart:

I see. So your interest really grew out of — I suppose it could have emerged at almost any time. There wasn’t any particular event in the rest of physics that stirred this to happen?

Dicke:

I think I viewed it as a tool, hoping to do some physics by looking at the universe. As far as geophysics is concerned, I think I was pretty well disillusioned on this, about mid-l960’s, I would say. This is another whole question, tangent, but long before the average geologist in the country took this continental drift, and plate tectonics’ to mean anything at all — Harry Hess, over in our geology department, had a clear picture of what was going on. Anyway, it’s obvious that as gravitation is getting weaker, the earth should expand slightly, and I noticed in my readings at that time that there were cracks in the mid-Atlantic ridge in the ocean, oceanic cracks. So this suggested that these cracks might be the result of tension, due to the earth expanding, and I made some [???] of this. I went over and talked to Hess about this. We laid out a beautiful picture of the Atlantic Ocean crust moving, and trenches, and island arcs, and all the — the whole plate Techtronic game was laid out for me, and this was the late fifties. He was way ahead of the rest of the boys; I don’t think actually that Hess received the credit that he deserves in this respect.

Weart:

It’s a whole other interesting story, this revolution in geophysics and the role that physicists may have played in it, also.

Dicke:

Well, this is not to say that a weakening gravitation and expanding earth might not play an interesting role in the evolution of the earth, but it just seemed to me to be so deeply buried in all the other things that it would be hard to separate it out, in an unambiguous way.

Weart:

Right.

Dicke:

I had one student, for example, look at the heat flow problem from this point of view, because you have heat flowing — if you have the interior hot, as we understand it is, and if the temperature curve for the mantle of the earth is near the melting point, if you lower the pressure inside, the melting point curve shifts, and heat has to flow out, or else the earth melts, one or the other. And you can calculate the way in which heat flows out this way. And it agrees rather well with what is observed, to a factor of two. So this could play a role. But you know, I decided after a while that it was just too hard to try to get fundamental physics out of the earth.

Weart:

Right. I understand. I understand very well,

Dicke:

But then there were a lot of implications for cosmology. I wrote a paper on a hot cosmology, in which scalar tensor theory is used, and you can see that, depending on the assumptions you make, you have a quite different early history of the universe. You can have a fireball expand without producing helium at all, for example. And under certain conditions, producing a little more than you would otherwise expect. There’s an interesting problem for the temperature history of the earth in this. In fact, I noticed a paper the other day, in which somebody else, somebody noted again that the problem that you face with the origin of life on the earth — if there isn’t any weakening gravitation — because the standard history for the way the sun evolves has it somewhat dimmer in the past — but if the oceans freeze, the earth is cold, and it’s hard to understand how life could arise under these conditions.

Weart:

Right. Of course, solar evolution is in quite a mire, right now.

Dicke:

That’s right.

Weart:

That’s another problem.

Dicke:

There could be other ways of explaining it.

Weart:

It sounds as if you have your finger in almost every one of the completely confused problems.

Dicke:

That’s right. Just about every confused problem I’ve worried about — without getting any real answers.

Weart:

Maybe you’ll all find the solutions at the same time.

Dicke:

Maybe.

Weart:

Well tell me, there’s a lot of things I could ask, but to get back to astrophysics and cosmology, I think a lot of people would agree that there’s been a very great upsurge in interest in general relativity within the last, I don’t know, since the fifties, I suppose. What would you say has caused this?

Dicke:

Well, I saw Shander [???] last week, and we were talking about this very problem. I had thought, and I think a lot of people think, that the new sources of observation are what stimulated the theorists to make real progress. And I don’t think that may be true. Shander, on the other hand, took the view that the new observations have played a rather minor role, that what had been important is the work of a few key individuals. He mentioned particularly the understanding of gravitational, radiation, of the — that it is a real effect — and so on — the work that Bondi did, in the early sixties. I remember when I first started going to relativity meetings, at international conferences and so on. There was a great deal of confusion about this. People had — some had gotten negative gravitational radiation dampings, some positive some didn’t get any at all.

Weart:

Negative gravitational —?

Dicke:

Yes. One of the well-known theorists in the country had a system where he had radiating negative energies. But the straightening out of that confusion, in his view, played a rather important role in getting things moving, understanding the initial value problem.

Weart:

This flowed out of — it probably did not depend too much on the new observations, from what you’ve said.

Dicke:

Well, certainly, as I said, I looked to the observations as a means of providing some clues as to whether there was a scalar component in gravitation or not. And this has been a confusing story, at best. It’s just confusing. I’m giving a talk this afternoon — talking again about the solar brightness problem, in relation to the other observations. The observations have come and gone. There are systematic errors, and they disappear.

Weart:

That‘s happened to a lot of things in cosmology, I think. Things that are just on the limit of detectability. Well, of course, the discovery of the microwave radiation.

Dicke:

I think that played a very key role. At the time, that this was done, there was a really large number of people that were taking the steady state universe seriously. I remember talking to Shombus (?) some years later, who was one of the strong advocates — a student of Fred Hoyle, who worked closely with him, something like that talking to him about the role of this discovery, and the way he put it was that, that when he threw over steady state cosmology and accepted the Big Bang, it was like putting on sackcloth and ashes. He became more conservative than conservative.

Weart:

There were a lot of people who felt that steady state theory was —?

Dicke:

— there were quite a few that took it seriously, I think. I don’t think it was a majority.

Weart:

Did you ever take it seriously?

Dicke:

I didn’t. No.

Weart:

You never took it seriously.

Dicke:

And the discovery of the black body radiation was another confused story.

Weart:

Right. I’ve read you — printed a once or twice, I guess. Made a story.

Dicke:

Yeah. That’s — if you want to know who to talk with about this, and try to get the story straight, I think first of all, Pensy? is one you should talk to. And then Wilkinson here, and Peevis. I think —

Weart:

Are you talking about the microwave theory, or about the whole?

Dicke:

The microwave theory.

Weart:

Who do you think would be good to talk to about, the whole general relativity? The whole general relativity, cosmology story?

Dicke:

Well, — you’re from Boston, is that right?

Weart:

I’m from New York, the AIP. But you know, I can get around.

Dicke:

I was thinking of someone who has not really played an active role in the cosmology, but nonetheless does know more than anyone, I think is Steve Weinberg — in connection with producing his book. You know his book?

Weart:

I’m not sure.

Dicke:

He seems to have read everything, —

Weart:

Oh, Gravitation and Cosmology.

Dicke:

For a theorist, for a particle theorist, he has developed a tremendous background, and — in cosmology. Just from his reading.

Weart:

He seems to know a lot of people, too.

Dicke:

Yes. So he would be a good one to get some leads from, I think. Now, as far as those who have worked in cosmology for a longtime, there’s Sandage, Allan Sandage. And relativity — I think John Wheeler is hard to beat. It’s hard to beat John Wheeler, for someone who’s been in the field for a long time and can give you some perspective about what has happened, if you could get him to talk about the historical development. Another one who could give your perspective, who’s been in it a long time, would be Peter Bergman. Peter, probably more than any person in the country, could be called Mr. Relativity, in the sense of having been working with it a long time, and active. Another one that has also been involved for a long time, although not active in a research way, is Hoffman.

Weart:

I didn’t realize that.

Dicke:

He was an assistant to Einstein in the thirties.

Weart:

That’s right. And he’s in New York. Who do you think have been the main contributors? These are people who would be good to talk to, but who do you think have been the big figures in the field? Would it be these same ones or others?

Dicke:

I would say, the primary contribution — the really central figure in this country, who has worked mainly through his students, is John Wheeler, more than anyone, I think. He’s been amazingly successful at attracting bright young people to work with him. And to what extent his students’ ideas, to what extent his — I think primarily, his ideas, that are then worked out through the students, — but the students go off, elsewhere. You can go down a list, one after another, the active contributors, the young people in the country now, are students of John Wheeler. So he is, in a sense, I think, Mr. Relativity, in terms of the modern developments.

Weart:

It’s true. True. I’m having lunch with him today, by the way, on Center business. I should talk with him about this more. What do you think have been the main centers? Princeton clearly, as you mentioned, but what other places?

Dicke:

Well, now a strong center is Cal Tech, with Kit Thorne. Another center is Chicago. Kit Thorne is one of John’s students, Chicago, with Geroch [?] who’s a student of John’s.

Weart:

How’s that spelled?

Dicke:

G-E-R-O-C-H. And also, Chadrasakhar has been involved in relativity in recent years. Then, Eric Dim? I was trying to, think of Burton’s students. University of Texas, where the DeWitt’s are, Bryce DeWitt — I think through Bergman, I’m not quite sure, got interested in relativity quite a long time ago. He’s been active in the field, probably as long as John Wheeler has. Peter Began and his students —

Weart:

Where is he?

Dicke:

Let’s see, I guess he’s actually retired now. But Syracuse and Yeshiva in New York.

Weart:

We’ve been talking I guess almost exclusively about the United States.

Dicke:

Oh, that’s true.

Weart:

We should mention some other places.

Dicke:

I don’t have a good perception of the foreign work, I think. There’s — Podanski is here, today, as matter of fact, from Poland. He is — now, let’s see, who was the famous Polish physicist that worked with Einstein? I’ve forgotten his name. He died a few years ago. There’s a group that built up in Poland, and. I can’t — Then there is, in Paris, from a rather mathematical point of view, — again, I’ve forgotten the fellow’s name. He’s strong in differential geometry. And his students — in Paris. But they’ve been rather mathematical. In England, — Synge, I think. In Denmark, Muller. This is really not a very good review. You‘d do much better asking John.

Weart:

OK, I should ask him about it. We’ve mostly been talking about — are there any specialists you know that have been mostly defined in groups that have dispersed or haven’t held up?

Dicke:

It’s been a rather developing field, and I think, the history in the last 20 years has been quite different — students going out and forming new centers, to the point where there are now dozens of centers in the country, and every one of these, you could say even, is enucleated by the students of one of the other — you know, principal centers. And I guess you’d have to say, the principal centers, if you go back 20 years, are Princeton and Bergman. Incidentally, one of the nice things about what Kip Thorne is doing, and his students, has been to be more directly concerned with the observations, not making formal mathematical theory, but to bring in the observations to test the theory, and to try to think through the theory with the observations.

Weart:

Yes, that’s true. Of course, that’s part of where they are, too — where the observations come in. (Cal Tech)

Dicke:

That’s certainly a part of it.

Weart:

Now, what about institutions in the broader sense? For example, you mentioned that there was a time when relativity conferences began to start up.

Dicke:

Well, there was an international organization of relativists, started about 1960 — perhaps 1960, somewhere in there. And that has met every two years since then.

Weart:

International, sometimes here, sometimes Europe, whatever.

Dicke:

Yes.

Weart:

What about in the departments — Let me switch this.... (Off tape) What about in the department here? Was there at some point when a relativity seminar, or something like that, began?

Dicke:

I’m trying to think how far back John’s interests went in relativity. I think he got started being interested in this somewhat before I did. I don’t have a clear memory of this now. But probably, a few years before. I can’t remember whether he had a relativity seminar going at that time, or whether it was started later. For a long time now, we’ve had a relativity seminar which meets Tuesday afternoon, and then a number of gravitation seminars and that sort of thing. Things have changed from time to time. We used to have two different seminars, and combined them. We’ve always had some kind of a seminar in relativity here, for more than 20 years.

Weart:

I see. Now, there was a series of Pixus (?) conferences.

Dicke:

Yes, they started — the first one of those was, I don’t know, eight years ago, maybe, ten.

Weart:

Do you know how they got started? What was involved there?

Dicke:

I think — see, what was the primary motivation? If I remember correctly, there was some rather important series of observations that got them interested. It was first devoted to astrophysics, and astrophysics that might have relativity implications. But it, whether it was started by the discovery of the pulsar, or whether it was before that, I’ve forgotten. I think it was motivated primarily by observations that were coming in. It was very successful and active, very large groups, for a while. I haven’t been myself, for the last couple. I don’t know quite how it’s going now.

Weart:

Speaking of observations and things, another question — you haven’t mentioned Joe Weber.

Dicke:

Yes.

Weart:

What kind of a role do you think all that has played?

Dicke:

I think that it’s probably played a very important role, in stimulating people to work in this area. It‘s a very imaginative technique, trying to see these very tiny effects in a huge bar and inspired people’s imagination. A rather large number have jumped into it. The fact that there have been several international conferences now devoted, in part at least, to these gravitational radiation problems —

Weart:

— “gravity waves,” whether or not they are there —

Dicke:

Yes.

Weart:

What is your feeling on that now, by the way? Has your feeling on that changed over the last ten years?

Dicke:

I — I don’t know. I’m not really close enough to have a good opinion, a strong opinion. But off-hand, it seems to me that the evidence is rather against it at this point. There have been a number of quite good experiments that failed to see gravitational waves. I was talking with Joe about these things last spring, and — when I was at Cal Tech — and he still very firmly believes that he’s seen the real thing, and the others haven’t built equipment enough to see it yet.

Weart:

Certainly, I remember, I was impressed, when I first saw how sensitive the darned things could be. That was the really unexpected thing for me, in this experiment. All right — another thing I wanted to ask you. What is your relationship with Brans was and is?

Dicke:

Oh. That’s an interesting one. I didn’t really supervise Brans’ thesis. Bran was a young theorist here, working with Charlie Misner, and Charlie didn’t have a problem for him to work on. So Charlie sent him to me, and I’d been thinking about this possibility of combining a scalar field with a temperature field, and suggested an action principle that he could investigate, and see what the field equations were, what the implications were. So he went off and worked on this with Charlie. Charlie, I gather, he didn’t really work with him either. He pretty well did it on his own.

Weart:

I see.

Dicke:

It was a rather straightforward mechanical thing, because you just had to calculate the equations. But there was one crucial point at which Charlie did play a role in it. Then, he came back with this, and he and I together, I guess primarily me, wrote that paper, which represents some contributions I made afterwards, sort of complex.

Weart:

How did you happen to think of the scalar field in the first place? I suppose, I haven’t looked into the history of it very clearly myself, but I know that there were an awful lot of different ideas floating around, different kinds of cosmologies. What brought your attention to the scalar field?

Dicke:

Well, it was just a feeling that I had, through Mach’s principle that the gravitational constant ought to be determined by the matter distribution in the universe, if you were going to make sense out of that, without imposing boundary conditions, and without imposing constraints, unreasonable constraints. And then, I recognized one day that, you could construct a theory in which the scalar field generated by the matter distribution in the universe could play the role of a reciprocal gravitational constant, of being a wave equation. And this suggested a very natural way of writing the — an action (?) principle.

Weart:

Tell me, I’ve gotten the impression from some of the things you’ve written, that you find this philosophically more interesting, or philosophically better than the field theory in which distribution of matter does not play a role?

Dicke:

Well, yeah. It seems to me, from a point of view, that you have two choices available to you. They really go back to the argument that Bishop Berkeley had with Newton, and their two ways of looking at things. You have the choice of assuming that you have a space which exists, and you put matter in this, and that the — such things as metric tensors and so on had meaning before you ever put the matter in. Now, the matter can influence the metric tensor, but you‘re not in the position of saying that the one exists by virtue of the other. Or, if you have an underlying frame of some kind in which matter moves, that’s one viewpoint, which was — comes back to the space of Newton. Then, the other viewpoint says that the whole thing is one physical system, that the tensor of gravitational theory is only one of many different kinds of fields, that it ties the whole thing together, but you don’t single it out for special treatment on the whole, so that tensor is the result of an interaction with the whole universe, if you like. That the whole thing is boot-strapped together.

Weart:

In a way, the metric tensor isn’t an underlying space, any more than you would say it for any other field.

Dicke:

In fact, a way of looking at this which I find very attractive and nobody else does is that you don’t treat the metric tensor initially as a metric tensor at all; you treat it just as a field that produces forces. And there aren’t any inertial forces, from that viewpoint. A particle moves the way it does because all the various kinds of forces which act on it balance out.

Weart:

This is Mach’s principle, in effect.

Dicke:

It’s effectively Mach’s principle. Now, it’s interesting, when you look at it that way, that formalism comes down to this — there are two reasonable possibilities, as far as formalism’s concerned. One is the straight Einstein theory, and the other is the scalar-tensor theory. If you take the viewpoint that its Einstein’s theories, then you have a situation where you start interpreting things, see. The structure of an atom, is the result of the various fields acting — electric field, electromagnetic field, and the tensor field, and then you recognize that the tensor field has the role of changing atoms — changing the structure of an atom from point to point. But if you interpret everything in the sense that the atom hasn’t changed, this carries with it the implication of a curved geometry. You measure the geometry with meter sticks, and clocks, constructed of these kinds of atoms, that geometry is a curved geometry. So the metric interpretation comes in through the back door.

Weart:

I see. When you’re talking about an atom changing, it’s like the idea of a metric stick stretching or whatever, that same idea. I see. But, do you feel that the scalar is necessary, to have a really, a very solid Mach’s principle in gravitational theory? Or can one —?

Dicke:

I think it is, but I’m a school of one, on this.

Weart:

Do you feel somewhat isolated from other physicists, by that?

Dicke:

On this particular problem — yes.

Weart:

Do you think that other physicists, cosmologists and so forth, have the same philosophical interests?

Dicke:

There are very few that are really interested in this, I think. John Wheeler’s quite interested in this, and I am, but the usual cosmologist is more interested in the observations and their interpretation, and the theoretical structure built usually with standard general physics.

Weart:

I see — not so interested in philosophy or the philosophical view of things.

Dicke:

Right. Also, I think one has to say this about cosmology, that, when I was a graduate student in the early fifties, it was cosmology and the cosmological models, structure of the universe and so on. In later years, there’s been a lot, of interest in other aspects of cosmology which are which have to do with the origin of the elements, fireball structure and its development — in homogeneities in the universe, and how they can lead to formation of galaxies, the whole problem in homogeneities, instabilities. So, instead of it being a global problem, the way it was, people are really much more cornered now with the nitty- gritty of how the elements came into being, and so on.

Weart:

That’s true; it’s more concerned with the contents of space than with space itself, if you like.

Dicke:

Yes.

Weart:

Do you feel that there’s been a corresponding change in the orientation of people? Were people more philosophical, back when they were, concerned with these global properties?

Dicke:

I think, when you have few observations, you can afford to be philosophical. It’s also been my observation, which may well be wrong, that the less you know about a subject, the mole strongly you believe in it, and feel about it. When there were few observations, people had very strongly entrenched positions.

Weart:

— as it gets more complicated, things begin to —

Dicke:

— that’s right, as soon as you have observations, then these preconceived notions begin to crumble.

Weart:

I guess that’s been the story of the whole development of the field, in the last 20 years. Things have gotten more and more complicated. It gets back to increasing complication. Tell me, what do you feel now about the solar oblateners? I remember very well when that first —

Dicke:

Well, I’m giving a talk this afternoon, discussing some work I did in California. There’s been a paradox connected with these observations, the last couple of years, that’s bothered me. Not because it seemed to invalidate the implication of the oblateners in any way, but because there was some piece of the results I didn’t understand. And when there’s any little piece you don’t understand, why, you can feel very uncomfortable. But I think I understand it now. This is a strange business that if you — these principal observations, of simple diagonal components — you expect the diagonal component of the oblateners to vary in a well-defined way through the season — the data fit that curve fairly well. But the residuals that you get would scatter around that curve. On the face of it, if you look at that scatter, you would say, that’s just plain noise. At the time that the data were first published, why, I thought they were due to bad seeing at Princeton. I’ll show you — scatter, around that curve —

Weart:

— right, yes, I remember that stuff — (Crosstalk)

Dicke:

— distribution there, if you look at the distributions quite Galson (?) I don’t know why I didn’t do it sooner, but when I finally got around to taking the correlation function of those residuals, I found they weren’t random. They were strongly periodic actually. There was a periodicity of 12 2/3 days — two-thirds — and this

Weart:

(???)

Dicke:

No. No, that’s the interesting thing; to actually discover what was going on there. But 12 2/3 days is obviously also periodic at 25 1/3 days. And I had interpreted it — I had first seen this periodicity that way. And then when I stacked the data, I discovered there was a double peak, there, which carried also the implication that that shorter period was in there. Well, I now have a rather — well, let me say this, that I couldn’t find any reasonable physical explanation for this, not in the, atmospheric parameters, not in the telescope (crosstalk) It had to be — and that 25 1/3 day period suggested a period of rotation. The interesting thing was that it was impossible to explain it that way. And the reason I thought it was impossible was that if you take this block of data, that’s symmetric, about this crossing point, the — and make the Fourier expansion of the disturbance, in that basic period, there it should be only odd harmonics.

Weart:

They’d be symmetrical, about —

Dicke:

And what you discover, when you do it, is all even harmonics.

Weart:

OK. So what’s the explanation?

Dicke:

Well, I had the wrong period. It’s actually the short period. Then you can account for the rigid rotation. And if you subtract out the effect of that rigid rotation, by being — it’s [???] like this.

Weart:

I see. It comes much closer to the —

Dicke:

(crosstalk) ... about how good you can account for it, this is the far spectrum. The solid lists are the far spectrum of the data themselves. The dotted curve is the far spectrum that you calculate from the model, of what — the distortion of the surface of the thing. The distorted surface rotating rigidly.

Weart:

A rigidly rotating distortion —

Dicke:

— distortion in the — rotating at 12 2/3 days, actually 12.

Weart:

(crosstalk) What could support a distortion?

Dicke:

Well, that’s an interesting story, too.

Weart:

I see, wait till you publish it — read it when you publish —

Dicke:

As a matter of fact, I don’t have that. I concentrated on statistics. I didn’t want to color statistics with —

Weart:

— right —

Dicke:

— notions, so it’s straight statistics, up to now. I’ve just started on the physics.

Weart:

Well, I gather you’re pretty excited about a rotating —

Dicke:

— well, I think, very likely the whole thing is right. It’s due to something rotating on the inside more rapidly than on the surface.

Weart:

Although 12 2/3 days is not quite —

Dicke:

It’s not the rapid rotation I was talking about.

Weart:

Right. But then, people haven’t detected very great frequency shifts or whatever near the sun, anyway.

Dicke:

Right.

Weart:

You don’t require at this point as rapid a rotation as you did at one point. Isn’t that right?

Dicke:

No, I still require — it’s going to be the inner half of the sun rotating, which is the source of the oblateners. Then I need about factor (?) 20, there, which is a little over a one day period.

Weart:

I see, so you just put it in there.

Dicke:

The other possibility on this, which is actually what fits this better, is a — making an internal magnetic field, which is starting to —

Weart:

Uh huh, I see that would make sense.

Dicke:

Rotating not as fast as — but —

Weart:

How are your feelings toward the solar oblateners theory, over the past ten years or whatever, since you first detected it?

Dicke:

I’m just struck by how, looking at the same data over and over again, you learn more and more about it. I’ve learned a lot more than I knew a year after it was — measurements were made.

Weart:

How have your colleagues reacted to your interest in these things?

Dicke:

I think that they — colleagues, while they have their own problems they’re worrying about — How do physicists and astronomers view this? I think they don’t believe it. But that doesn’t matter. That doesn’t influence me particularly. After all, I have to deal with the data. I’d like to say that you don’t settle a scientific question by taking a popularity poll. That’s not the way you settle it. That’s like establishing pi by going out on the street and asking little boys how much pie is. One says 47, one says 4, one says half — and you take an average.

Weart:

I always said, that when you wrote a book, you should write it for the largest possible audience, which didn’t mean the number of people who would read it next year, but the number of people who would read it over the next thousand years.

Dicke:

That’s right. No, I’m not being swayed in my interpretation of these data by what people think, in the slightest.

Weart:

Tell me something else, too. Here you’re in the physics department and you’ve been going, I guess, almost from the start, when you first came back from the Rad Lab, you started doing studies of microwaves and what not — what has been the feeling in the physics department about someone who does things that are not what would be narrowly considered physics, but a more —?

Dicke:

Well, I have a — that’s a very interesting question, and I should answer it I think by telling you that when I came from the Radiation Lab here, I didn’t realize what the situation was. I brought with me a radiometer, a microwave radiometer, and was interested in getting into the radio astronomy business. That was 1946, which would have been the first one in this country. But I thought, you know, you’re an assistant professor, you’re doing such offbeat, wild things — you wouldn’t last here six months. I couldn’t really do that, was my view. So I went over to our astronomy department and tried to interest them in a joint venture of some kind, thinking this would give it a little more respectability. And I couldn’t get any interest over there. So I didn’t do this. I actually scavengered the equipment and started using, it for laboratory experiments. Well, it took a few years, and I realized that that was a completely wrong approach. This department is so tolerant, I could have gone into radio astronomy and there wouldn’t be an eye batted about it. It was an interesting question, though, in that connection. I wasn’t concerned about this department at all, but I was a little worried, when we started getting interested in astrophysics, in our research group, how the astronomers would view that. So I went over and talked to a couple of senior astronomers, and they said, “The more the merrier.” So we have a sort of a strange situation now, where we have a very sizeable part of the total ‘astrophysics effort right in this physics department, with former students of mine. Jim Peebles is one of my students. Dave Wilkinson didn‘t come in as a student, but he came in as a young colleague. So, it’s a little bit anomalous, from the standpoint of the structure of the university, but it seems to cause no problems.

Weart:

Both the astronomers and the physicists are glad to have you around?

Dicke:

Astronomy students come over to work with Jim Peebles occasionally. And I think some of our students then go over and do — teach in the astronomy department.

Weart:

This is one of the things that I’m particularly interested in, this whole development over the last twenty year’s or whatever — to show how the physicists and the astronomers have started to merge into one another. I gather from what you said, they were pretty separate when you first came back.

Dicke:

Well, as far as structure’s concerned, it’s very separate. The astronomers, the last thing in the world they would want would, be to have any formal connection with us. They view themselves as a small department, few students, and they think they would be swallowed up in the superior thing, if there were any formal structure. So there isn’t that. But when it comes to day to day interaction, there’s no problem. Our students are interchanged, and —

Weart:

— at what point did you start interacting with the astronomers here?

Dicke:

Oh, about the time when I began to see the implications of a scalar field for astronomy. The evolution of a star, for example. A star would be brighter in the past, according to scalar tensor theories, and lead to its burning its fuel more rapidly. This would mean that the implications for stellar age and stellar evolution would be different. And that sort of thing. Then I went over and started talking with Schwarzschild first — that was perhaps in the early sixties, late fifties.

Weart:

Well, we’ve pretty well covered the ground, I think. Do you think of anything else? As you said over the phone, there’s a lot of other things that I could ask you, but just in terms of astronomy, we can stop here.

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